image/apng

Animated PNG — Mozilla's answer to animated GIF, folded into the official PNG specification in its third edition after years as an unofficial extension. An APNG is byte-for-byte a valid PNG with an extra acTL chunk before the image data, so it shares PNG's exact signature and cannot be distinguished by magic bytes alone; decoders that predate it simply show the first frame. Send it when you need lossless animation with alpha, though animated WebP or AVIF is usually smaller.

.apng distinguishes files on disk, but plenty of animated PNGs ship as plain .png — the extension is a hint, not a rule.

Defined by W3C PNG (Third Edition) · IANA registration. Registry facts from the IANA media-types registry via mime-db.